Battery comprising positive electrode composed of principal and secondary active material wherein sole electronic path is through the secondary active material

ABSTRACT

A battery electrode composed of a principal active material and a secondary active material and a method of discharging the same so as to achieve the discharge potential characteristic of the secondary active material wherein the sole electronic path for discharge of the principal active material is through the secondary active material. The discharge product of the secondary active material must be readily oxidized by the principal active material.

' United States Patent [72] Inventor Luis Soto-Krebs Santiago, Chile[2]] Appl. No. 445,904 [22] Filed Apr. 6, 1965 [45] Patented Oct. 26,1971 [73] Assignee ESB Incorporated Philadelphia, Pa.

[54] BATTERY COMPRISING POSITIVE ELECTRODE COMPOSED OF PRINCIPAL ANDSECONDARY ACTIVE MATERIAL WHEREIN SOLE ELECTRONIC PATH IS THROUGH THESECONDARY ACTIVE MATERIAL 50 FieldofSearch .......'.I..' 1367630, 183,102, 120,100,20,23,28,107,115, 111

[56] References Cited UNITED STATES PATENTS 2,542,710 2/1951 Ruben136/107 2,795,638 6 1957 Fischbach 136/120 Primary Examiner-Winston A.Douglas Assistant Examiner-A. Skapars Attorneys-Alfred J. Snyder, Jr.and Robert H. Robinson ABSTRACT: A battery electrode composed of aprincipal ac- I tive material and a secondary active material and amethod of discharging the same so as to achieve the discharge potentialcharacteristic of the secondary active material wherein the soleelectronic path for discharge of the principal active material isthrough the secondary active material. The discharge product of thesecondary active material must be readily oxidized by the principalactive material.

PATNTEnnm 26 I9?! SHEET. 10F 2 .FigZ

Fig I Time Hours Time Hours Time Hours SHEET 2 OF 2 PATENTEDUBT 2s |97lTime Hours l BATTERY COMPRISING POSITIVE ELECTRODE COMPOSED OF PRINCIPALAND SECONDARY ACTIVE MATERIAL WHEREIN SOLE ELECTRONIC PATII IS THROUGHTIIE SECONDARY ACTIVE MATERIAL Certain battery applications require asubstantially constant voltage during discharge. Other applicationsdemand a particular discharge voltage. Most applications dictate thatthe battery supply a maximum capacity while simultaneously restrictingits size and weight. The problem of furnishing a battery for a givenapplication is complicated by the fact that while some electrode activematerials have inherently good capacities, they discharge at two or morepotentials. Moreover, those materials which are most active and hencemost desirable for battery use characteristically discharge at severalvoltage levels, thus making their use impracticable. Still other activematerials which have good capacities and substantially constantdischarge voltages, discharge at potentials which may not be suitablefor a particular application.

It is, accordingly, a general object of the present invention to providea new and improved electrode construction characterized by an increasein capacity per unit weight and volume.

It is another object of the present invention to provide electrode meansfor utilizing an active material at the lower potential'of a secondactive material.

It is still another object of the present invention to provide electrodemeans for achieving a single potential discharge from a multivalentoxide, such as divalent silver oxide, that discharges at two or morepotentials. It is a further object of the present invention to providean electrode having two different active materials which will'utilizethe capacity of both materials at the potential of the lower potentialmaterial.

' It is still a further object of the present invention to provide a newand improved button-type cell construction.

While not limited thereto, the principle of the. present invention canbe illustrated by means of a divalent silver oxide electrode whichdischarges at two different potentials. During the initial discharge. ofsuch an electrode, the divalent silver oxide is reduced to monovalentsilver oxide. Theoretically, this reaction proceeds until all of thedivalent silver oxide has been reacted. Next the monovalent silver oxideis further reduced to metallic silver. The first reaction, whiledivalent silver oxide is present, provides an open circuit potential, inan alkaline electrolyte of approximately 1.8 volts vs. zinc. The secondreaction, while monovalent silver oxide is present, provides an opencircuit potential in an alkaline electrolyte of approximately 1.6 voltsvs. zinc.

In practice, due to such effects as polarization and the masking of thedivalent oxide by the formation of monovalent oxide, before a divalentsilver oxide cell is halfway through its useful life, its output voltagewill drop 0.2 volts. Many types of battery-operated electronic equipmentcannot tolerate a voltage change of this magnitude. A divalent silveroxide electrode in accordance with the present invention, however, willdeliver all of its capacity at the monovalent potential, thus providinga substantially constant output voltage.

To achieve a lower potential discharge from an active material inaccordance with the present invention, three conditions must be met.First, the discharge product of the lower potential active material mustbe readily oxidizable in the battery electrolyte by the higher potentialactive material. Second, the higher potential active material must be inelectronic contact with the lower potential 'material. Third, thedischarge circuit must have electronic connection only with the lowerpotential active material.

Divalent silver oxide and monovalent silver oxide are examples of activematerials which satisfy the first condition stated above. The dischargeproduct of the lower potential active material, monovalent silver oxide,is metallic silver. Metallic silver is readily oxidizable by the higherpotential active material, divalent silver oxide, to monovalent silveroxide. The second and third conditions are achieved in accordance withthe present invention by a novel electrode structureutilizing as theprincipal active material a body of divalent silver oxid having thereonas the secondary active material a layer of monovalent silver oxide. Theelectrode contactmeans, that is, the electrical path for the dischargecircuit is in contact only with the monovalent sllvcr oxide layer.

While the prcscnl invention has been described hcrcmlwfore in connectionwith divalent silver oxide-and monovalent silver oxide, the principlesare applicable to other electrode active materials. Generally stated,the present invention provides a method of operating a battery at alower potential than that normally developed by the principal activematerial. This method comprises withdrawing current from the principalactive material through a current path consisting solely of aninterposed layer of secondary active material of a lower potentialhaving a discharge product which is readily oxidized by the principalactive material. The lower potential achieved from the electrode is thatdeveloped by the interposed layer of the secondary active material.Stated another way, the method of the present invention comprisesmaintaining electronic contact during discharge between the principalactive material and the discharge circuit only through the secondaryactive material.

By way of example of the applicability of the present invention to otheractive material, manganese dioxide can be discharged at the lowerpotential of copper oxide. Similarly, divalent silver oxide can bedischarged at the potential of copper oxide as well as at thepotential'of lead dioxide. 'Potassium permanganate can be discharged ata lower potential such as that of monovalent silver oxide or copperoxide. These examples are illustrative of only a few electrodecombinations which are possible by means of the present invention.

A better understanding of the present invention may behad from thefollowing description when read with reference to the accompanyingdrawings of which:

FIG. 1 is acurveshowing the theoretical discharge characteristics of asilver-zinc primary cell using as the active material of the positiveelectrode monovalent silver oxide;

FIG. 2 is a curve showing the theoretical discharge characteristics of asilver-zinc primary cell identical to the primary 'cell of FIG. I butusing as the positive active material'an equal volume of divalent silveroxide;

, FIG. 3 is a curve showing the theoretical discharge characteristics ofa silver-zinc primary cell identical to the cells of FIGS. 1 and 2, butusing a positive electrode in'accorda'nce with the present invention;

FIG. 4 is a cross-sectional view of a primary silver-zinc cell havingcomposite positive silver electrode in accordance with the presentinvention;

FIG. 5 is a top elevation taken along the line 5-5 of FIG. 4;

FIG. 6 is a cross-sectional view of an electrode in accordance with thepresent invention whereinthe isolating layer of secondary activematerial is formed by the in situ reduction of the principal activematerial by the'metal of the inner surface of the electrode cup;

FIG. 7 is a partial sectional elevation taken along the line 7-7 of FIG.6 and enlarged;

FIG. 8 is another partial sectional elevation taken along the line 7-7of FIG. 6 illustrating a modification of FIG. 7;and

FIG. 9 is a curve showing the discharge characteristics of an actualprimary silver-zinc cell in accordance with the present inventioncompared to the discharge characteristics of another cell of the sametype but incorporating a positive electrodecomprising an equal volume ofmonovalent silver oxide.

As indicated hereinbefore, both the broad and specific features of thepresent invention can be illustrated in connection with a positivesilver electrode. The capacity in milliampere hours per gram and thespecific gravity of both divalent and monovalent silver oxide are givenin the following table:

TABLE I Monovnlent Silver Oxide Divalent Silver Oxide (Ago) 433 7.44

. per gram than the monovalent oxide and has 1.95 times more capacityper unit volume than the monovalent oxide. The signilicance of thisbecomes apparent with reference to FIGS. 1 and 2. FIG. 1 shows atheoretical discharge curve of a conventional silver-zinc primary cellusing monovalent silver oxide as the positive active material. FIG. 2shows the theoretical discharge curve of a similar cell utilizing anequal volume of divalent silver oxide as the positive active material.Both of the discharge characteristics shown represent continuousdischarges through a 300-ohm load at 73 F. Obviously, the cell of theFIG. 2, the cell utilizing divalent silver oxide as the positive activematerial, has substantially more usable capacity thanthe cell in FIG. 1.However, while the divalent silver oxide cell has significantly morecapacity than the monovalent silver oxide cell, its discharge ischaracterized by, two distinct voltage plateaus. One, at approximately1.72 volts and the other at approximately 1.5 volts. Many batteryapplications, particularly transistorized devices such as hearing aids,cannot tolerate a voltage drop such as is exhibited by the cell of FIG.2.

The electrode structure of the present invention is designed to providemeans for utilizing the capacity of an inherently high-capacity materialsuch as divalent silver oxide at the potential of a second materialhaving a lower potential such as monovalent silver oxide. Referring toFIG. 3, there is shown the theoretical discharge curve of a silver-zinccell identical to those shown in FIGS. 1 and 2, except that it utilizesan electrode of the present invention. The curve of FIG. 3 is plottedfor discharge conditions identical with FIGS. 1 and 2. As shown by thiscurve, the cell exhibits a single potential discharge at the monovalentoxide potential level while utilizing the capacity of divalent silveroxide at that lower potential.

Referring now to FIG. 4, there is shown a sectional elevation of asilver-zinc primary cell, designated by the numeral 1, having a positiveelectrode in accordance with the present invention. The cell 1 isconventional in all respects with the exception of the construction ofthe positive electrode. The cell 1 has a two-part container comprisingan upper section or cap 2 which houses the negative electrode, and alower section or cup 3 which houses the positive electrode. As shown,the bottom cup 3 is fonned with an annular shoulder 4 having a flange 5which is crimped inward during assembly to seal the cell. The bottom cup3 may be made of nickel-plated steel, and the cap 2 may be made oftin-plated steel. The cap 2 is insulated from the cup 3 and the flange 5by means of a grommet 7 which is compressed between the cap 2 and theflange 5 during the crimping operation of cell assembly to provide acompression seal between these parts. The grommet 7 may be made of asuitable resilient electrolyte-resistant material such as neoprene.

The negative electrode of the cell 1 comprises a lightly compactedpellet 8 of finely divided amalgamated zinc. The zinc electrode 8 isseparated from the positive electrode by means of anelectrolyte-absorbent layer 9 and a membrane barrier 10. Theelectrolyte-absorbent layer 9 may be made of electrolyte-resistant,highly absorbent substance such as matted cotton fibers. Such a materialis available commercially under the trademark Webril. The barrier layer10 may be a suitable semipermeable material such as cellophane. orcomprise a suitable organic carrier such as polyethylene or polyvinylchloride having a polyelectrolyte homogeneously dispersed therethrough.Such a material is described and claimed in US. Pat. No. 2,965,697,issued Dec. 20, 1960, to .l. C. Duddy.

The positive electrode of the cell 1 comprises, in accordance with thepresent invention, a first pellet ll of the divalent silver oxide whichis surrounded on the bottom and side surfaces by a layer of monovalentsilver oxide 12. The pellet ll of divalent silver oxide is the principalactive material and comprises the majority of the active material in theelectrode available for discharge. The layer of monovalent silver oxide12 is the secondary active material. As shown in FIGS. 4 and 5, thelayer 12 of monovalent silver oxide isolates the pellet of divalentsilver oxide from all electronic contact with the bottom cup 3 which isthe positive terminal of the cell and the electrode contact. I

This electrode may be formed in a number of ways. For ex ample, thepellet 11 may be fonned by pelletizing finely divided divalent silveroxide powder in a suitable die. This pellet may then be centered in abigger pellet die, and finely divided monovalent silver oxide powdercompressed around it to form the composite pellet of the type shown inFIGS. 4 and 5. It is possible also to form the electrode by pelletizinga suitable quantity of divalent silver oxide powder and then chemicallyreducing its surface to the monovalent oxide. In addition, wheredesired, the surface layer of the divalent silver oxide pellet can bereduced to metallic silver and that layer subsequently reoxidized tomonovalent oxide. Electrochemical reduction can also be utilized toreduce the surface layer of a divalent silver oxide pellet to themonovalent oxide. It should be noted that the thinner the layer ofmonovalent silver oxide the more divalent oxide can thus be included inthe electrode increasing its capacity. However, under no circumstancesshould there be a discontinuity in the monovalent oxide layer whichwould provide direct electronic contact between the divalent oxide bodyand the discharge circuit. Such a discontinuity would cause theelectrode to discharge in the conventional manner with two voltageplateaus.

Referring now to FIG. 6, there is shown another embodiment of theelectrode of the present invention in which the monovalent silver oxidelayer is formed in situ by a chemical reaction between the divalentoxide pellet and a metallic coating on the electrode cup. Specifically,the inner surface of the cup 3 is plated with a layer 13 of a metalwhich will be oxidized by divalent silver oxide. As shown in FIG. 7 thisreaction will leave a layer of the metal oxide 14 and a layer ofmonovalent silver oxide 15 between the divalent oxide pellet l l and themetal plating 13 on the can 3. The inner surface of the cup 3 is platedprior to cell assembly. When the divalent oxide pellet 11 is placed inthe cup 3 it oxidizes the surface of the plated layer 13 in the cup 3 itoxidizes the surface of the plated layer 13 to form thereon a film 14 ofthe oxide of that metal and simultaneously a layer 15 of monovalentsilver oxide is reduced on the adjacent surface of the divalent oxidepellet 11. When this reaction is complete, the monovalent silver oxidelayer 15 completely isolates the divalent oxide pellet 11 from allelectronic contact with the metal oxide layer 14 and hence the cup 3.The presence of electrolyte absorbed throughout the pellet 11 willpromote the. reaction. By this method, it is possible to obtain thethinnest possible monovalent oxide layer and, hence, to include in thecell the greatest possible amount of divalent silver oxide. Severalmetals have been found to be suitable for plating the inner surface ofthe cup 3 to produce the -isolating monovalent silver oxide layer. Theseinclude zinc, copper, nickel and silver.

The use of zinc for the plated layer 13 has several advantages in asilver-zinc cell system. First, it introduces no foreign ions into thecell. More important, however, the zinc oxide layer is readily formed inthe presence of an alkaline electrolyte and provides an extremely lowelectrical resistance between the cup 3 and the pellet 11.

When nickel is used for the plated layer 13,.its surface is oxidized bythe divalent silver oxide to form a layer of nickel oxide which isconverted by the electrolyte to nickel hydroxide. Both the nickelplating and the nickel hydroxide layer are good conductors. However, thereaction between the divalent Silver Oxide and the nickel is slow andrequires cell aging before discharge to allow the monovalent silveroxide layer to form and completely isolate the divalent silver oxidepellet. In this respect, a two-weeks stand at room temperature has beenfound satisfactory for the formation of the isolating monovalent silveroxide layer. The reaction between the nickel and the divalent silveroxide is accelerated by heat and the cell aging time can be reduced withhigher aging temperatures. Care must be taken, however, not to exposethe cells to temperatures which will cause the reduction of the divalentsilver oxide in the cell to monovalent silver oxide.

Silver may also be used to produce the plated layer 13 provided thethickness of the layer is carefully controlled. Referring again to FIG.7, the reaction between a silver-plated layer 13 and the divalent silveroxide pellet 11 will produce a monovalent silver oxide layer 14 on theplated silver layer 13 and a monovalent silver oxide layer on thesurface of the divalent silver oxide pellet 11. The monovalent silveroxide layer 15, because of its permeability to electrolyte, is a lowresistance layer. The monovalent silver oxide layer 14, however, havingbeen produced by the oxidation of a metallic surface lacks ionicpermeability, and, as a result, forms a high resistance layer. Unlessthe thickness of the monovalent silver oxide layer 14 is limited,intemal cell impedance rises to a point where the usefulness of the cellbecomes very limited. By way of illustration, cells which normally wouldhave internal impedances of 5 ohms have been found to develop internalimpedances in the neighborhood of 300 ohms as the monovalent oxide layer14 grows.

The resistance of the monovalent oxide layer 14 can be kept low bypreventing it from developing to any substantial thickness. Toaccomplish this, the silver plated layer must be no more than a fewmolecular layers in thickness and of such character that it issubstantially totally consumed by oxidation reaction producing amonovalent oxide layer 14 of limited thickness. When the thickness ofthe plated layer is properly limited, the monovalent silver oxidelayer14 will have the low resistance required for practical cellapplications. This is shown schematically in FIG. 8 where the platedlayer 13 is completely oxidized in the formation of the monovalentsilver oxide layer 14 and disappears. The monovalent silver oxide layer15 on the divalent silver oxide pellet 11 is developed as before.

In manufacturing electrodes of the type where the isolating monovalentsilver oxide layer is producedby in situ reaction between a plated layer13 and the divalent silver oxide pellet ll, care must be taken that thedivalent silver oxide does not puncture or in any other manner disruptthe metal-plating layer and establish direct contact with the cup 3.This is particularly true with the case of a silver where the thicknessof the plated layer must be extremely thin. As stated hereinbefore, ifdirect electronic contact is established with the divalent silver oxide,the conventional two-voltage-plateau discharge will be obtained "ratherthan the monovalent oxide potential discharge which characterizes thepresent invention.

The cures of FIG. 9'demonstrate the increase in capacity actuallyavailable from a cell in accordance with the present invention. In thisFigure Curve A is the discharge curve of a conventional silver-zinccell, and Curve B is the discharge curve for a cell having a positiveelectrode in accordance with the present invention. The cellconstruction utilized in both cells was that shown in FIG. 4. Thenegative electrodes of both cells comprised lightly compacted batterygrade metallic zinc amalgamated with 14 percent mercury. The cells weresealed with neoprene rubber grommets. In both cells the separationbetween the electrodes comprised a layer of Webril absorbent and a 3-millayer of membrane made in accordance with the teachings of theaforementioned US. Pat. No. 2,965,697. The electrolyte absorbent layerwas saturated with an electrolyte formulated by dissolving 100 grams ofpotassium hydroxide and 16 grams of zinc oxide in I00 cc. of water.

The positive electrode of Cell A comprised 1.73 grams of commerciallyavailable battery grade monovalent silver oxide compressed into a pellet0.1 inches thick and 0.485 inches in diameter. The positive electrode ofCell B, the cell in accordance with the present invention, comprised acentral pellet containing 1.2 grams of divalent silver oxide 0.085inches thick and 0.387 inches in diameter. This central pellet wassurrounded by 0.6 grams of monovalent silver oxide which was compressedto provide a composite pellet 0.l thick and 0.485

inches in diameter. The divalent silver oxide mix from which the centralpellet was compressed comprised 96 grams of a specially preparedlow-gassing divalent silver oxide, and 4 grams of lead dioxide to whichthere was added 3.5 cc. of the electrolyte described hereinbefore foreach I00 grams of the dry mix.

Both cells showed an open circuit voltage of 1.58 to I59 volts and eachhad an impedance lower than 6 ohms. The curves of FIG. 9 are for acontinuous discharge of the cells through a 300-ohm resistance at atemperature of 73 F. As shown from these curves, Cell B, the cell inaccordance with the present invention, exhibited approximately 30percent more useful capacity than an identical size cell of theconventional monovalent silver oxide type. Of equal importance is thefact that this increase in capacity is achieved without the usualtwo-voltage-plateau discharge usually associated with divalent silveroxide.

Electrodes in accordance with the present invention have beenconstructed using electrode materials other than divalent and monovalentsilver oxides. For example, divalent silver oxide has been discharged atthe potential of 0.9 volts vs. zinc through a 300-ohm load at 73 F. byusing cupric oxide as the second electrode material. The cupric oxidecomposite electrode was constructed by mechanically pressing finelydivided cupric oxide around a pellet of divalent silver oxide. Anothercupric oxide divalent silver oxide electrode was constructed in a mannersimilar to the electrode in FIG. 6. In this electrode the inner surfaceof the bottom cup of the cell was plated with copper which wassubsequently oxidized to cupric oxide in the presence of. potassiumhydroxide electrolyte by the divalent silver oxide pellet.

Other electrode combinations are available. For example, manganesedioxide which has a potential in alkaline electrolyte vs. zinc of L5volts may be discharged at the potential of cupric oxide. Such amanganese dioxide cupric oxide electrode has been constructed anddischarged in accordance with the present invention by first pelletizinga small pellet of manganese dioxide and then compressing around thepellet an outer layer of finely divided cupric oxide. This electrode wasdischarged against zinc through a 300-ohm load at 73 F. at 0.9 volts. 71

Some examples of electrode combinations which may be constructed inaccordance with the present invention together with open circuitvoltages for such electrodes in alkaline electrolyte are listed in thefollowing table:

TABLE II Primary Active Material Secondary Active Material In each casethe primary active material must be able to oxidize the dischargeproduct of the secondary active material. If the materials chosen meetthis requirement and the primary active material is in electroniccontact with the secondary. active material while the discharge circuithas electronic connection only with the secondary active material asdescribed, the electrode will discharge only at the lower potential ofthe secondary active material.

From the foregoing, it can be seen that by means of the novel method andthe unique electrode structure described, there has been providedelectrode means for achieving a single potential discharge from anelectrode-active material such as divalent silver oxide which dischargesat two potentials. in addition, it is possible to utilize the capacityof an electrodeactive material at the lower potential of a second activematerial Of equal importance is that the method and the electrodeconstruction of the present invention provides the means for controllingwithin certain limits the discharge potentials of active materials. Thisnot only provides flexibility in cell design, but in many instances,also a means for achieving higher capacity cells than heretofore havebeen available. in considering the present invention, it also should benoted that, while zinc electrodes have been used as reference electrodesand for the negative electrode of the specific cells described, this hasbeen done for the purpose of illustration only and not by way oflimitation. An electrode in accordance with the present invention may beutilized in cells where the electrode of the opposite polarity is of anyconventional type.

Having described this invention, that which is claimed as new is:

1. In a battery having a positive electrode, a negative electrode, andan electrolyte, the improvement comprising a positive electrode having aprincipal active material which is manganese dioxide, a secondary activematerial which is cupric oxide and an electrical contact means, said twoactive materials being geometrically arranged in such a manner that saidsecondary active material is interposed between said principal activematerial and said electrical contact means as a continuous layer inphysical and electrical contact with said principal active materialphysically isolating principal active material from said contact means,said secondary active material having a lower potential than saidprincipal active material and a discharge product which in the presenceof the electrolyte is oxidized by said principal active material to forma secondary active material adjacent to the interface with saidprincipal active material, said oxidation reaction proceeding at ahigher rate than the reaction between the principal active material andthe negative electrode, said electrode being sufficiently porous topermit electrolyte to be present at the site of said reaction betweensaid principal active material and the discharge product of saidsecondary active material, said battery having an output voltagethroughout discharge of said two active r naterials characteristic ofthe couple formed by said secondary active material and said negativeelectrode.

2. In a battery having a positive electrode,,a negative electrode, andan electrolyte, the improvement comprising a positive electrode having aprincipal active material which is potassium permanganate, a secondaryactive material which is an oxide selected from the group consisting ofcupric oxide and monovalent silver oxide, and an electrical contactmeans, said two active materials being geometrically arranged in such amanner that said secondary active material is interposed between saidprincipal active material and said electrical contact means as acontinuous layer in physical and electrical contact with said principalactive material physically isolating principal active material from saidcontact means, said secondary active material having a lower potentialthan said principal active material and a discharge product which in thepresence of the electrolyte is oxidized by said principal activematerial to form a secondary active material adjacent to the interfacewith said principal active material, said oxidation reaction proceedingat a higher rate than the reaction between the principal active materialand the negative electrode, said electrode being sufiicientlyporous topermit electrolyte to be present at the site of said reaction betweensaid principal active material and the discharge product of saidsecondary active material, said battery having an output voltagethroughout discharge of said two active materials characteristic of thecouple formed by said secondary active material and said negativeelectrode.

3. In a battery having a positive electrode, a negative electrode, andan electrolyte, the improvement comprising a positive electrode housedin a cathode cup the principal active material of which consists ofdivalent silver oxide and the remaining active material of whichconsists of a continuous layer of monovalent silver oxide in physicaland electrical contact with said divalent silver oxide, said layer ofmonovalent silver oxide physically isolating said divalent silver oxidefrom contact with said cathode cup, said layer of monovalent silveroxide being disposed against the inner surface of said cathode cup whichinner surface is wet by said electrolyte and consists of a metal capableof being oxidized by said divalent silver oxide in the presence of saidelectrolyte, said layer of monovalent silver oxide being formed on saiddivalent silver oxide as a result of said divalent silver oxide beingdisposed against the inner surface of said cathode cup, which innersurface consists of a layer of a metal selected from the groupconsisting of zinc and copper, and said battery being characterizedthroughout discharge by a potential characteristic of monovalent silveroxide.

4. In a battery having a positive electrode, a negative electrode and anelectrolyte, the improvement comprising a positive electrode having anelectrical contact means housing a principal active material whichconsists essentially of a first metallic oxide and a secondary activematerial which consists essentially of a continuous layer of a secondmetallic oxide in physical and electrical contact with said firstmetallic oxide, said layer of second metallic oxide physically isolatingsaid first metallic oxide from said contact means which comprises thesole electronic contact with said active materials, said layer of secondmetallic oxide being disposed against the inner surface of said contactmeans which inner surface is wet by said electrolyte and consists of ametal different from the metal of said first metallic oxide, the metalof said inner surface being capable of being oxidized by said firstmetallic oxide in the presence of said electrolyte, said layer of saidsecond metallic oxide being formed on said first metallic oxide as aresult of said first metallic oxide being disposed against the innersurface of said contact means, and said battery being characterizedthroughout discharge by a potential characteristic of said secondmetallic oxide and said negative electrode in said electrolyte.

5. A battery in accordance with claim 4 in which the first metallicoxide is divalent silver oxide and the second metallic oxide ismonovalent silver oxide.

i i I

2. In a battery having a positive electrode, a negative electrode, andan electrolyte, the improvement comprising a positive electrode having aprincipal active material which is potassium permanganate, a secondaryactive material which is an oxide selected from the group consisting ofcupric oxide and monovalent silver oxide, and an electrical contactmeans, said two active materials being geometrically arranged in such amanner that said secondary active material is interposed between saidprincipal active material and said electrical contact means as acontinuous layer in physical and electrical contact with said principalactive material physically isolating principal active material from saidcontact means, said secondary active material having a lower potentialthan said principal active material and a discharge product which in thepresence of the electrolyte is oxidized by said principal activematerial to form a secondary active material adjacent to the interfacewith said principal active material, said oxidation reaction proceedingat a higher rate than the reaction between the principal active materialand the negative electrode, said electrode being sufficiently porous topermit electrolyte to be present at the site of said reaction betweensaid principal active material and the discharge product of saidsecondary active material, said battery having an output voltagethroughout discharge of said two active materials characteristic of thecouple formed by said secondary active material and said negativeelectrode.
 3. In a battery having a positive electrode, a negativeelectrode, and an electrolyte, the improvement comprising a positiveelectrode housed in a cathode cup the principal active material of whichconsists of divalent silver oxide and the remaining active material ofwhich consists of a continuous layer of monovalent silver oxide inphysical and electrical contact with said divalent silver oxide, saidlayer of monovalent silver oxide physically isolating said divalentsilver oxide from contact with said cathode cup, said layer ofmonovalent silver oxide being disposed against the inner surface of saidcathode cup which inner surface is wet by said electrolyte and consistsof a metal capable of being oxidized by said divalent silver oxide inthe presence of said electrolyte, said layer of monovalent silver oxidebeing formed on said divalent silver oxide as a result of said divalentsilver oxide being disposed against the inner surface of said cathodecup, which inner surface consists of a layer of a metal selected fromthe group consisting of zinc and copper, and said battery beingcharacterized throughout discharge by a potential characteristic ofmonovalent silver oxide.
 4. In a battery having a positive electrode, anegative electrode and an electrolyte, the improvement comprising apositive electrode having an eLectrical contact means housing aprincipal active material which consists essentially of a first metallicoxide and a secondary active material which consists essentially of acontinuous layer of a second metallic oxide in physical and electricalcontact with said first metallic oxide, said layer of second metallicoxide physically isolating said first metallic oxide from said contactmeans which comprises the sole electronic contact with said activematerials, said layer of second metallic oxide being disposed againstthe inner surface of said contact means which inner surface is wet bysaid electrolyte and consists of a metal different from the metal ofsaid first metallic oxide, the metal of said inner surface being capableof being oxidized by said first metallic oxide in the presence of saidelectrolyte, said layer of said second metallic oxide being formed onsaid first metallic oxide as a result of said first metallic oxide beingdisposed against the inner surface of said contact means, and saidbattery being characterized throughout discharge by a potentialcharacteristic of said second metallic oxide and said negative electrodein said electrolyte.
 5. A battery in accordance with claim 4 in whichthe first metallic oxide is divalent silver oxide and the secondmetallic oxide is monovalent silver oxide.